JPS60150628A - Photoelectric detector - Google Patents

Abstract

PURPOSE:To avoid an erroneous detection due to dirt, etc. by a method wherein, in a photoelectric detector for relative alignment device of two items such as mask and wafer in a semiconductor baking device, the photoreceiving surface of a photodetector is divided into two surfaces i.e. for detecting pattern and for receiving scattering light. CONSTITUTION:A photodetector 18 is composed of the photoreceiving surfaces 18a, 18b1-b4, 18c1-c4, 18d1-d4, 18e1-e4 respectively divided to receive signals independently. The central photoreceiving surface 18a receives the normal reflecting light of photoscanning beams. In such a constitution, it is recognized that photoscanning beams are scanning the detecting region while enabling synchroneous signals to be transmitted from a postprocessing circuit and reflecting power of a detected item to be measured. When a mark pattern 12a is detected, the sum of signals transmitted from the photoreceiving surfaces 18b1, 18c1, 18d1, 18b3, 18c3, 18d3, 18e3 will become the mark signals while the sum of signals transmitted from the photoreceiving surfaces 18b2, 18c2, 18d2, 18e2, 18b4, 18c4, 18d4, 18e4 will become the noise signals. When the mark signals and the noise signals are detected by said procedures, any noise signal synchronized with the amount almost similar to that of scattering light due to dirt, etc. contained in the mark signals may be detected easily.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to the relative alignment of two objects such as a mask and a wafer in a semiconductor printing apparatus, or the photoelectric detection of an alignment apparatus for processing machines such as semiconductor devices. The present invention relates to a photoelectric detection device, and particularly to a photoelectric detection device that is effective for detecting a detection object whose surface is not flat but uneven, or a signal whose diffraction pattern is known in advance.

[Prior art]

As a conventional photoelectric detection device, JP-A-56-017-A (Model Deposit 1 Special Chuei Station) +y? There is a device related to the present applicant that has been reported to be of great concern. In this device, a light shielding member is arranged to remove specularly reflected light from a flat object surface and receive only necessary pattern scattered light. Is the size of this light shielding member as large as possible to block specularly reflected light?
Or set it slightly larger than that.

However, if the surface of the object is not flat but uneven, scattered light will occur in areas other than the predetermined detection marks, and the light cannot be blocked by the light shielding member.This causes a decrease in the contrast of the detected light and reduces the detection accuracy. Problems such as deterioration or undetectability were occurring.

In addition, as a photoelectric detection device according to the conventional example, Japanese Patent Application Laid-Open No. 531
There is a device according to the applicant disclosed by No. 35.654. In this device, the detection light beam is divided into two using a d light beam splitting means, each detection light beam is selectively transmitted using a predetermined spatial filter, and these two transmitted lights are received by another light receiving element. The configuration is such that the pattern signal is converted into an electrical signal, and the electrical signal is processed to selectively detect a pattern signal.

However, according to this configuration, since the detection light beam is divided into two parts and detected, the light intensity of the detection light beam is halved in the light receiving element, and a chisel turn with low reflectance or a chisel turn with a low wafer level difference is sufficient. The drawback was that it could not be detected.

Furthermore, unless the central axes of the plurality of spatial filters are precisely aligned with the central axis of the detection light beam, there is a problem in that the contrast of the detection light beam decreases and the detection accuracy deteriorates.

The present invention has been proposed in view of the drawbacks of the above-mentioned conventional examples, and it is a photoelectric detection device that makes it possible to obtain a detection signal with an optimal S/N ratio and contrast ratio, or a spatial filter that can be aligned in a similar manner. Another object of the present invention is to provide a photoelectric detection device that makes it possible to obtain a predetermined detection signal by changing the filter range of a spatial filter.

〔Example〕

Hereinafter, a photoelectric detection device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a principle diagram of a signal detection system of an automatic mask and wafer alignment apparatus to which a photoelectric detection device according to an embodiment of the present invention is applied. 1 is a laser light source 22 is a condenser lens.

6 is a rotating polygon mirror, 4 is a relay lens, and 5 is a beam filter 2 for dividing the light into 22 or less visual optical systems.
6 is a field lens, 7 is a beam series for dividing light into 14 or less photoelectric detection optical systems, 18 is a relay lens, 9 is a beam series for guiding light from illumination optical systems for visual observation from 19 to 21. Tsuta-910 is the objective lens 11
12 is a mask, and 16 is a wafer. The conjugate relationship of the laser beam itself is as follows.

That is, the laser beam is focused at a position 60 by the condenser lens 2. The spot diameter of the laser beam at the position 60 is determined by the diameter of the incident laser beam and the focal length f2 of the condenser lens 2. Assuming that the laser beam is uniformly distributed within the diameter, the diameter d of the laser spot is given by . The laser beam diverging from the position 60 is reflected by the rotating polygon mirror 6, passes through the relay lens 4, and -
An image is formed at a point 62 near the tan field lens 6.

Further, the light passes through the relay lens 8 and the objective lens 11 and is imaged at 64 positions corresponding to the mask and wafer surfaces. Therefore, 30 and 62.34 in FIG. 1 are conjugated to each other. The diameter Φ of the spot 64 that actually scans the mask and wafer surfaces is expressed as Φ=aXd, where a is the imaging magnification of 60 to 64. The scanning spot diameter can be changed by changing d and can be achieved by changing the beam diameter of the laser beam or the focal length f2 of the lens 2. If only the scanning spot is to be enlarged, this can also be achieved by intentionally moving the position of the condenser lens 2 and defocusing the laser beam at position 60. Generally, it is desirable that the diameter of the scanning spot be appropriately selected depending on the target ξ-turn line width, but the system shown in FIG. 1 can easily cope with changes in the spot diameter. The condensing mask and the wafer surface are scanned at position 64.

In addition to the conjugate relationship of the scanning beam on the actual object plane as explained above, the image formation relationship of the pupil of the optical system shown in FIG. 1 is also important. The pupil of the objective lens 11 is indicated by 10, and a point 66 on the optical axis, which is the center point of 10, and a reflection point 61 of the rotating polygon mirror 6 are conjugate with each other. In other words, in terms of the incidence of the laser beam on the objective lens, the arrangement shown in FIG. 1 is equivalent to placing a rotating polygon mirror at the position of the pupil 10.

A telecentric objective lens is used when observing reflective objects such as wafers. Objective lens 11 in FIG.
is a telecentric arrangement, that is, the pupil 10, which determines the light beam passing through the optical system, is placed at the front focal position of the objective lens 11.

Figure 2 shows this situation. The center 66 of the pupil position 10, which is the front focal point of the objective lens 11, is conjugate with the laser reflection position 61 of the rotor A as described above, so the scanning beam acts as if the scanning beam was generated from here. The principal ray, which is the center line of the main ray, passes through the front focal point 66 of the objective lens, so after passing through the objective lens 11, it becomes parallel to the optical axis and enters the mask and wafer perpendicularly. If the area drawn by the scanning beam is flat, the incident light will be reflected and return to position 66 again. On the other hand, if there is a pattern where the scanning beam hits, the light will be scattered at the edges of the pattern boundaries and will not return to its original location. That is, when the scattered light is captured by the objective lens 11 and passes through the pupil 10 again, it no longer passes through the center 66 of the pupil but passes toward the edge of the pupil.

This simply means that scattered light and non-scattered light are spatially separated by absorption. FIG. 2 shows this separation. That is, if the scanning beam scans the object surface from left to right, the light is not scattered until it hits a certain part 65 of the pattern and is reflected to the pupil 10.
Return to the original location. When the light hits the pattern 65, it is scattered and does not return to its original position on the pupil 10 through the optical path shown by the dotted line.

The area occupied by the unscattered light at lf[10 is the same as the effective diameter of the scanning laser beam. In order to effectively capture scattered light,
The effective diameter of this non-scattered light is normally set to be sufficiently small relative to the diameter of the pupil, and the ratio of this diameter is usually 0.1 to 0.
It is preferable to keep it in the range of 7.

Returning to FIG. 1 again, consider the photoelectric detection optical system that separates from the beam splitter 7 and reaches the photodetector 18. In the figure, 14 is a lens that forms an image of the pupil 10 of the objective lens 11, and 15 is a filter that transmits light for photoelectric detection but substantially cuts other wavelengths, such as wavelengths used in the viewing optical system.

The position of the photodetector 18 is where the image of the pupil 10 is formed by the pupil imaging lens 14. Therefore, the pupil 10° photodetectors 18 are in a conjugate relationship with each other. This photoelectric detection system produces an output only when the scanning spot approaches the detection object. Therefore, by observing the output over time, it can be seen that a pulse-like signal is generated when the scanning beam hits an edge, and a step-like signal is obtained when the scanning beam hits the sensing object. If this pattern is a signal from an alignment/mention mark on the mask and wafer, the relative positional shift between the mask and the wafer can be detected from this signal. Auto-alignment is performed by moving the relative positions of the mask and wafer using a drive system (not shown) so as to correct the detected amount of deviation. Further, a step-like signal generated when the scanning beam hits a detection object is used as a synchronization signal.

In FIG. 1, illumination systems 19 to 21 and observation systems 22 and below are provided for visual observation. 19 in the figure is a light source for illumination,
A condenser lens 20 functions to form a light source image on the pupil 10 of the objective lens 11.

Reference numeral 21 denotes a filter that has the function of cutting off light in the wavelength range to which the photoresist is sensitive. On the other hand, 22 is a filter for normal rotation of the image, and an erector 126 is a filter that cuts the laser wavelength and transmits the wavelength for visual observation, and 24 is an eyepiece lens.

On the other hand, an example of a mark suitable for laser spot scanning is found in, for example, "Optical Device" filed by the applicant on January 22, 1978. This mark is a mark like the one shown in FIG. 6 that can detect x and y deviations in one direction line scanning. Figure 6(a)
(b) is a pattern for a mask (or wafer), (b) is a nog turn for a haueno-(also a mask), and (c) is the state when both are aligned 7 times. Note that the dotted line in Figure (C) is the locus of the scanning laser beam.

As described above, one of the problems with the photoelectric detection method is dust. In other words, since this photoelectric detection system detects scattered light, if there happens to be a substance that scatters light, such as dust, in the area targeted for photoelectric detection, the scattered light of this dust will be picked up as a signal. Dust may be attached to the wafer or inside the scanning optical system. It can be said that dust adhering to the wafer is a factor that must always be taken into account1.Detected light from other than the pattern generated in this way is a false signal, which is not only undesirable, but can also cause malfunctions. .

The present invention is aimed at removing unwanted detection light from other than patterns such as the above-mentioned dust or diffused reflection from the surface of a detection object. Specifically, the present invention includes means for dividing the light receiving surface of a photodetector. It is intended to be utilized.

Here, in order to utilize the means of dividing the light-receiving surface of the photodetector, we will use the photodetector 1 of the photoelectric detection section shown in Figure 1.
Consider the distribution of light observed at point 8. In the explanation so far, scattered light has been understood as a phenomenon of scattering from pattern edges, but in other words, this is nothing but a type of diffraction phenomenon. Therefore, light is scattered in a direction that depends on the directionality of the pattern. Figure 6 ((In the case of the alignment mark shown, the distribution of scattered light observed at the position of the photodetector 18, the so-called diffraction pattern, is shown in Figure 4 (a).
, (1)) K is shown. The fact that the scattered light extends in a direction perpendicular to the direction in which the pattern extends is easily explained by the theory of normal diffraction phenomena. Figure 4 (a) is Figure 6 12a,
4fb) is the scattered light from 12c, 13b, and 12d in FIG. 6. On the other hand, scattered light from irregularly shaped substances such as dust does not show any particular directionality at the light shielding plate and spreads uniformly. The situation is shown in FIG. 4(C). Figure 4 (a), (bl, (C1) The black dot in the center is the area of non-scattered light, and the other shaded areas indicate the area where the light is spreading. indicates the effective diameter of this optical system.

The present invention utilizes the difference in scattering from the [ξ-turn portion and the non-pattern portion at the photodetector position. Therefore, in the present invention, the special enemy is to divide the light receiving surface of the photodetector to provide a pattern detection light receiving surface and a scattered light receiving surface. The roles of these light-receiving surfaces are switched depending on the direction of the detection pattern. (Here, the signal obtained from the pattern detection light receiving surface is called a mark signal, and the signal obtained from the scattered light receiving surface is called a noise signal.) FIG. 5 is a schematic top view showing an embodiment of such a photodetector. It is. The 18 photodetectors are each divided into light receiving surfaces 18a, 1. from which signals are extracted independently. ．． 8
b+, 18b2, 181) 3, 18b, .

18c, , 18c, , 18Cs, 18c, ,
18d+, 18d2.

18ds, 18d4.18c+ +1se2, 18e
s, 18e4. The central light receiving surface 18a receives specularly reflected light of the optical scanning beam. This makes it possible to recognize that the optical scanning beam is scanning the detection area, generate a synchronization signal by the post-processing circuit, and measure the reflectance of the detection object. When detecting the mark patterns 12a, 13a, and 12b in FIG. 6, the light receiving surface i8b
, + 18C+ + 18d1t i8e+ 118
The sum of the signals obtained from b3118C3, 18d3, and 18ea becomes the mark signal, and the light receiving surface 18bt, 1
8c, , 18dz.

18e2 +18b, 1iac4+18d4, +18
The sum of the signals obtained from e4 becomes the noise signal. Next, mark patterns 12c, 13b, 12d in FIG.
When detecting, the light receiving surfaces 18b2, 18C2, 18
d2, 18e2゜18b4, 18C4, 18d4,
The sum of the signals obtained from 18e+ becomes a mark signal, and the light receiving surfaces 18bI and 18CI.

I Bd+ + 18e+ + 18bs + 18C
The sum of the signals obtained from a r 18ds 118es becomes a noise signal.

When mark signals and noise signals are detected in this way,
It is possible to detect a noise signal that is synchronized with approximately the same amount of light scattered by dust or the like contained in the mark signal. Therefore, by subtracting the noise signal from the mark signal, there will be no erroneous detection due to dust or the like, making it possible to completely eliminate such effects. Here, the side where the mark signal is output is called the A channel, and the side where the noise signal is output is called the B channel. Since the pattern direction of the marks and patterns shown in Figure 6 is known in advance, by detecting the synchronizing signal and counting the number of pulses detected by the post-processing circuit, it is possible to determine which direction the light-receiving surface will be the A channel. , or the B channel.

Next, a signal processing system according to an embodiment of the present invention will be explained. FIG. 6 is a signal diagram for explaining the signal processing. FIG. 6(a) shows the positional relationship between the patterns on the mask and the wafer when they are scanned. In this figure, the dashed line indicates the laser scanning light, and the arrangement is exactly the same as in FIG. 6(C) except that the dust 42 is on the scanning line.

Figure 6 (b) shows the output of the A channel, and Figure 6 (C>) shows the output of the B channel.The A channel is the detection channel for "pattern + dust J", and the B channel is the detection channel for "dust", so as shown in the figure. The output will be

FIGS. 6(d) to (e) show three aspects of the signal that has passed through a differential amplifier (not shown) that performs the calculations (A, -B). (
d) is when the A channel's garbage signal and B channel's garbage signal cancel out exactly, (e) is when the B channel's garbage signal is larger, and (') is when the A channel's garbage signal is larger. This is a case where complete cancellation cannot be achieved.Which of (d) to (f) ((this depends on the characteristics of dust scattering, applying a magnification to one or both signals during differential amplification, or There are various factors involved, such as using sensitivity differences between detectors, so it cannot be determined in general. However, it is possible to simply cut only non-scattered light (
Compared to the output of bl, the signals (d) to (f) after passing through the differential amplifier suppress noise by 1, and the pattern S/N
increasing the ratio.

Next, another problem with photoelectric detection is that if the surface of the target area for photoelectric detection has unevenness, the scattered light generated by the unevenness will be picked up as a signal. is a decrease in contrast, S/N
This results in deterioration of detection accuracy and signal detection rate.

Considering the distribution of scattered light from the unevenness on the surface of the photoelectric detection target area observed at the photodetector 18 in FIG. 1, this scattered light has a special directionality at the detector, -18. It shows a uniform spread. Figure 4 (
d) is a state in which there are some irregularities on the surface of the detected object.If the irregularities are slightly thicker, it becomes Fig. 4 (e), and when the unevenness becomes even larger, it becomes Fig. 4 (fl).In this way, the surface of the detected object becomes The spread of scattered light also changes depending on the unevenness. Figure 4 (d)
), (el, and (f)), the black dot in the center is the area due to non-scattered light, and the other shaded area shows the area where the light is spreading.The outer circle is the effective diameter of this optical system. It shows.

The present invention focuses on the difference in the spread of light at the position of the photodetector 18. Therefore, in the present invention, 4
The light-receiving surface of the photodetector extending in the direction is divided into four light-receiving surfaces in each direction at equal distances from the center.

For signals from the light-receiving surfaces in each direction, light-receiving surfaces equidistant from the center are selected in response to differences in signal levels due to differences in patterning and spread of scattered light from the surface of the detection object. After each output signal of the selected photosensitive surface is combined,
The best contrast and S/N ratio is then output as a signal to the signal processing circuit.

FIG. 7 is a block diagram of a signal processing circuit according to an embodiment of the present invention. Light-receiving surface 1 in the center of photodetector 18
When 8a detects that the detection scanning beam is scanning within the detection area, it outputs a signal to that effect to the amplifier 51. The amplifier 51 amplifies the signal and then outputs it to the torque comparator 58 and the ψ converter 54. The signal from the light receiving surface 18a output to the converter 54 is converted into a digital signal and sent to the arithmetic processing circuit 57. The arithmetic processing circuit 57 includes an arithmetic processing section, a memory section, and an interface section that handles input/output signals. ~ Φ converter 54 The signal of the first scanning beam inputted to arithmetic processing circuit 57 is detected by the arithmetic processing circuit, and after calculating and determining the threshold level, D/A converter 5
Output to 6. The threshold voltage output from the D/A converter 56 is used as a reference voltage for the voltage comparator 58. The voltage comparator 58 compares this reference voltage with the output of the amplifier 51 by the second scanning beam, and outputs a signal while the detection scanning beam scans the detection area. This output signal is shown in FIG. 8(d),
This output signal is used as a synchronization signal for time measurement of a pattern signal, which will be described later.

Each light receiving surface 18bl, 18C, of the photodetector.

18d, , and 18e+ are selection switches 50b+ and 18e+, respectively.
50c, .

It is connected to the signal synthesis circuit 52 through 50dl and 50e1. Similarly, other light receiving surfaces are also connected to the signal combining circuit 52 via corresponding selection switches.

Each selection switch is turned on or off according to the output of the arithmetic processing circuit 57, thereby selecting each light receiving surface.

The signal synthesis circuit 52 has an amplifier for each light receiving surface, and has an adder and a subtracter that independently add or subtract signals from each light receiving surface according to the output of the arithmetic processing circuit 57, and combines them. voltage comparator 59 as one output.
and can be output to an A/D converter (equipment).

The arithmetic processing circuit 57 first outputs an ON output to the all selection switch so that the signals of all the light receiving surfaces are input to the signal synthesis circuit 52.

Next, the arithmetic processing circuit 57 sends the signal synthesis circuit 52 to the light receiving surfaces 18b, , 18C+ +18dl, ise, +
18b3 +18Cs + 13c13118e3 signals are added, and the light receiving surfaces 18b2, 18C2, 18d
2.1se2,181)4.18C4,18d4゜18
Give a command signal to subtract the signal from e4.

The signal synthesis circuit 52 outputs the added/subtracted output to the A/D converter 56 and the voltage comparator 59. The arithmetic processing circuit 57 passes this output through the A/D converter 56, detects the magnitude of the signal, calculates and determines a threshold level, and outputs it to the D/A converter 55. The voltage comparator 59 connects the input from the signal synthesis circuit 52 and the D/
The threshold pressure from the A converter 55 is compared and a pulse output corresponding to the /ξ turn signal is output.

Then, the arithmetic processing circuit 57 counts the number of pattern signals of the voltage comparator 59 from the time when the synchronization signal of the voltage comparator 58 is generated, and after counting 6 pattern signals and passing the 93rd .xi. turn signal, A command signal for addition and subtraction is given to the signal synthesis circuit 52.

That is, the light receiving surface 181)2 + 18C2r 184
+ 18e2 +isb, , 18C4, 18d4
, 18e4 are added, and the light receiving surface tab, +
isc, +18d4 + i8e+ 18bs +
18cs +18ds r The signal from 18 e s is subtracted. As a result, the obtained signal synthesis circuit 5
The output of 2 is shown in FIG. 8 fbl. This signal synthesis circuit 52
The addition/subtraction process and the combination of light receiving surfaces are switched and repeated at the rising edge of the synchronizing signal and when six pattern signals are counted, as described above.

By the way, the signal shown in FIG. 8(b) contains a lot of scattered light due to the unevenness of the detection surface. The arithmetic processing circuit 57 is A, 4)
The output of the signal synthesis circuit 52 via the output of the converter 56,
In other words, as shown in FIG. 8 (the signal of bl is taken in and stored in the storage section of the arithmetic processing circuit, and the sdestal signal P1 and pattern signals Sl, 52tSs jS4 jS, , S, are calculated.) If the ξ turn signal is large or When the death signal P1 is larger than a certain value, the arithmetic processing circuit 5
7 is the inner light receiving surface 18b, , 18b2°1 ab3.
a selection switch 50b to disconnect the signal of 18b4;
, 50b, , 50b8, and 5Db4 to prevent them from being combined by the signal combining circuit 52.

The output of the signal synthesis circuit 52 obtained as a result is shown in FIG.
It will look like C1. Detector 1 as shown in Figure 8(C)
If the inner light-receiving surface of 8 is separated, the death signal P2 will be significantly reduced, but the pattern signal S? rS8 +SOr
SIQ r SII r "12 also decreases. In this way, the arithmetic processing circuit 57 separates the light-receiving surfaces of the photodetector one by one, fixes the combination of light-receiving surfaces that provides the best contrast when the pattern signal is above a certain level, and at the same time In response to the decrease in the nomiturn signal level, the voltage comparator 5
The threshold voltage to 9 is also changed. Next, the arithmetic processing circuit 57 detects the outer light receiving surfaces 18e, 1ae2.18es of the photodetector 18 while confirming that the contrast does not deteriorate beyond a certain level.

The light-receiving surface is separated from the combination 18e4, and the separation of the light-receiving surface is stopped one step before the contrast deteriorates beyond a certain level.

Generally, when the operation of separating the light from the outside is performed, there are cases where no effective light beam is incident on the light receiving surface on the outside, but even in such a case, a dark current flows. This is because this dark current is a noise signal and substantially reduces the S/N ratio. By appropriately combining the light-receiving surfaces of the photodetectors 18 in this way, the best contrast, the best S/N, and therefore the best pattern signal can be obtained. As a result, a signal with a good detection rate and high detection accuracy can be obtained.

FIG. 8(a) shows the positional relationship when the patterns on the mask and wafer are scanned, and the dotted lines indicate laser scanning. FIG. 8(b) is a detection signal diagram when all the light-receiving surfaces are activated, (C1 is a detection signal diagram when the light-receiving surfaces are optimally selected and combined, and (d)
l is a synchronization signal diagram.

〔Effect of the invention〕

As explained above, according to the present invention, the photoelectric elements are arranged corresponding to the diffraction direction of the detection nomiturn and are also divided in the radiation direction, and a predetermined signal is detected by a selected combination of each photoelectric element. Therefore, there is no need to divide the detection light beam into two as in the conventional case. Therefore, it is possible to obtain a detection signal level that is large enough to reduce the amount of light by half.

Since there is only a single signal detection route, the device configuration is simplified. Furthermore, complicated positioning such as optical axis alignment of a plurality of spatial filters is unnecessary, and distortion adjustment is simple. Since each photoelectric element is on the same plane, the sensitivity among the elements is uniform.

Further, according to the present invention, optimum contrast and optimum S
Since a plurality of divided light receiving surfaces can be appropriately selected so as to obtain a detection signal having a /N ratio, detection accuracy and signal detection rate can be improved.

Further, according to the present invention, the photoelectric element is divided into a part for detecting a pattern signal of a detection object and a part for detecting that a detection area surface is detected, and the photoelectric element is divided into a part for detecting a pattern signal of a detection object and a part for detecting that a detection area surface is detected. It can be used as a synchronization signal and a threshold voltage for signal detection, and has the effect of shortening detection time and simplifying the device configuration.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a signal detection system of a four-mask and wafer automatic alignment device to which a photoelectric detection device according to an embodiment of the present invention is applied, FIG. 2 is a diagram showing the action of a telecentric objective lens, and FIG. The figure is a diagram showing an example of marks used in the automatic alignment device. Figure 4 is a diagram showing the diffraction pattern from the mark and the distribution of scattered light from the surface of the detection object, Figure 5 is a diagram showing a photodetector according to an embodiment of the present invention, and Figure 6 is a diagram showing the present invention. A signal diagram for explaining a signal processing system according to an embodiment of
FIG. 7 is a block diagram of a signal processing circuit according to an embodiment of the present invention, and FIG. 8 is a diagram showing a detection mark pattern, a detection signal before and after selection of a light-receiving surface, and a synchronization signal according to an embodiment of the present invention. . 1...Laser light source 2.4, 6, 8, 14.20.22.24...Lens. 6... Rotating polygon mirror 5.7.9... Beam series 10... Pupil 11 of objective lens 11... Objective lens 12... Mask 16... Wafer 15.21.23... - Filter 18... Photodetector 19... Light source for illumination 65... Pattern depression 51... Amplifier 52... Signal synthesis circuit 53.55... D/A converter 54.56... ~ Width converter 57... ... Arithmetic processing circuit 58.59 ... Voltage comparator. Figure 2 Figure 1 JD Fh3FM Figure 4 Figure 5 Cause

Claims (1)

[Claims] A photoelectric detection device comprising a plurality of photoelectric elements capable of receiving diffracted light having directionality according to a detection pattern and arranged so as to be divided with respect to the radiation direction of the direction.